Instead of seeing the person at the face value of their despicable beliefs, try to see what's really going on in their minds and find within it a bridge towards commonality.
Those who believe in genocide see those they wish to kill as dehumanized vermin, why? Because they don't know them, because they've never had a conversation with them, because they feel threatened by them.
Make someone feel safe, and enable them to communicate with each other, make them see the shared humanity, and I believe the vast majority would change their minds.
